Preheat your air fryer to 330 degrees F (165°C) for 3-5 minutes. Whisk the flour, milk, eggs, salt, and melted butter in a large mixing bowl until smooth. The batter should be thin and pourable.
Generously grease the cups of a popover pan or a muffin tin with cooking spray or oil. Grease the sides and bottoms thoroughly to prevent sticking.
Fill each cup of the popover pan or muffin tin about three-quarters full with the batter. Do not overfill, as the popovers will expand during baking.
Carefully place the filled popover pan or muffin tin in the preheated air fryer basket. If your air fryer has a small capacity, you may need to bake the popovers in batches.
Air fry the popovers at 330 degrees F (165°C) and set cook time for 20-25 minutes or until they are puffed up and golden brown outside. Avoid opening the air fryer basket during baking to prevent the popovers from deflating.
Once the popovers are done baking, remove them from the air fryer and immediately transfer them to a wire rack to cool slightly. This helps prevent them from becoming soggy.